What does this plastic part do? - PeachParts Mercedes-Benz Forum

benhogan · #1 03-02-2010, 06:46 PM

On the W126 front passenger footwell. If you remove the floormat, there is a black rainbow shaped vent looking duct.

Does anyone know what it is for? I suspect rainwater is getting into the car via that duct.

Is it possibly the source of my water leak?

I have cleaned the sunroof drains. However, water still gets in somehow. It only gets wet in the rear passenger footwell very close to the driveshaft hump under the front seat.

Any ideas are more than welcome. I would like to remove the plastic duct to double check. Thank you very much in advance!

Phil · #2 03-02-2010, 07:16 PM

If you are talking about the flat plastic cover it covers the wire and vacuum tube channel. You can lift the side and look in it.

SD Blue · #3 03-02-2010, 09:04 PM

Under the floormat?

Could you be talking about the heater duct for the rear seats?

deanot442 · #4 03-02-2010, 09:07 PM

my vote is for the rear heat duct

compu_85 · #5 03-02-2010, 09:44 PM

Sounds like the rear air vent to me too. I would look elsewhere for the leak. I had the same problem and found a rust hole in the rain tray

-J

Codifex Maximus · #6 03-03-2010, 12:21 AM

Make sure rain water is not accumulating in your cowl vents. In my W123, the outlets on the firewall were clogged allowing water to backup into the ducting, soaking the passenger floorboards and ruining an expensive blower motor. Not sure if your W126 has a similar layout but worth looking into.

benhogan · #7 03-03-2010, 08:10 AM

Quote:

Originally Posted by Codifex Maximus

Make sure rain water is not accumulating in your cowl vents. In my W123, the outlets on the firewall were clogged allowing water to backup into the ducting, soaking the passenger floorboards and ruining an expensive blower motor. Not sure if your W126 has a similar layout but worth looking into.

I have a feeling that it is the cowl vents. Even though the holes are small, the damn pine needles still manage to get it.

Thanks for the input guys.

300dOwner · #8 03-03-2010, 08:40 AM

Had the same problem on my w123, cowl vents plus the area behind the battery was packed with leaves etc. Water pooled in the passenger rear footwell...I discovered the leak when my father in law was wondering why his feet were getting soaked

... well I guess there's a bright spot to every needed repair

brandlj · #9 03-03-2010, 08:46 AM

The circular duct you are refeering to is the heat duct for the rear passenger's feet. It goes up under the seat. If you slide the passenger seat forward, you will see the outlet for the heat.
I had a similar water leak in my 1986 300sdl. It turned out to be the foam hose that drains your evaporator core for your air conditioning. On the front transmission tunnel there are two drain hoses, one on the driver's side and one on the passenger's side. They attach to the drain pan for the evaporator and then drain through a hole in the floorboard.. The original hoses are made of foam with a wire coil in it to keep it from collapsing. Over the years the foam disintegrates and they leak water when you have the A/C on. The water then travels along the transmission hump and pools under the rear carpeting. The reacement hoses are identical in construction. I did not like them and replaced them with rubber hoses that will not deteriorate.
I would look under the front carpets on both sides and check out those hoses.

Good Luck

brandlj · #10 03-03-2010, 09:08 AM

I would also remove the battery and the battery tray. Vacuum all the junk out and you may find a rust hole under all of the junk under the battery. That would allow water to drain right into the area in the passenger front footwell, and then it can pool under the seat.

benhogan · #11 03-03-2010, 09:26 AM

Quote:

Originally Posted by brandlj

The circular duct you are refeering to is the heat duct for the rear passenger's feet. It goes up under the seat. If you slide the passenger seat forward, you will see the outlet for the heat.
I had a similar water leak in my 1986 300sdl. It turned out to be the foam hose that drains your evaporator core for your air conditioning. On the front transmission tunnel there are two drain hoses, one on the driver's side and one on the passenger's side. They attach to the drain pan for the evaporator and then drain through a hole in the floorboard.. The original hoses are made of foam with a wire coil in it to keep it from collapsing. Over the years the foam disintegrates and they leak water when you have the A/C on. The water then travels along the transmission hump and pools under the rear carpeting. The reacement hoses are identical in construction. I did not like them and replaced them with rubber hoses that will not deteriorate.
I would look under the front carpets on both sides and check out those hoses.

Good Luck

Brandj,
Thanks for the tips. Stupid question but what if the AC in my car does not work. Would I get the same symptoms when it rains.

The localized area where it gets wet is the area closest to the hump by the rear mount for the passenger seat.

SD Blue · #12 03-04-2010, 02:09 AM

The a/c drain hoses are on each side of the transmission tunnel. The drivers' side is right next to the accelerator pedal and the passenger side is just opposite.